We propose to accumulate operations experience with a combined gas chromatograph-mass spectrometer and with high pressure liquid chromatography instruments for application to the analysis of small samples of human blood for the presence of 24-, 25-, and 26-hydroxycholesterol derivatives. We further seek to determine whether there are correlations between the levels of these sterols in human plasma and human cardiovascular disease, particularly atherosclerosis, hypertension, heart attack, etc. We currently seek to establish definitively that the named sterols indeed are present in human plasma and that methods for their analysis can be operated.